Error when decoding base64 with buffer. First argument needs to be a number

I am working on running different encoding statements based on the URL.

My code:

  var parsedUrl = url.parse(req.url, true);
  var queryAsObject = parsedUrl.query;

  var myString = queryAsObject["string"];
  var myFunction = queryAsObject["function"];

  if (myFunction == "encodeb64") {

  var bufEncode = new Buffer(JSON.stringify(myString));
  var myEncode = bufEncode.toString('base64');

  console.log(myEncode);

  }

  else {
    console.log("Error1");
  };


  if (myFunction == "decodeb64") {

  // var bufDecode = new Buffer(myEncode, 'base64');
  // var myDecode = bufDecode.toString('utf8');

  var myDecode = new Buffer(myEncode, 'base64').toString('utf8');

  console.log(myDecode);

  }

  else {
    console.log("Error2");
  };

URL used: http://127.0.0.1:8020/?string=text&function=decodeb64

The issue is that I am having is with the last if statement. If its looking for decodeb64 and the first statement is looking for encodeb64 it crashes when function=decodeb64 is in the URL. If both if statements are looking for either encodeb64 or decodeb64, it runs perfectly. It also works if function=encodeb64 is in the URL.

The error message I get is:

buffer.js:188
        throw new TypeError('First argument needs to be a number, ' +
              ^

It points to:

  var myDecode = new Buffer(myEncode, 'base64').toString('utf8');

The given number on the error is pointed to the n in new.

I have located the problem to be inside the decode if statement by moving and reversing the order on the code.

As you can see in my code notes, I have tried two different methods of decoding with no success.